Abstract:

A printing or embossing unit has at least two cylinders (1, 2). Of the
latter, one working cylinder (1) carries at least one printing or
embossing stencil (14) on its circumference, in order to emboss or to
print, with the aid of the said at least one printing or embossing
stencil (14), a web (5) made from a flat material which is conveyed
between the said working cylinder and a back-pressure cylinder (2). The
embossing stencil (14) extends in each case only over part of the
circumference of the working cylinder (1) and is held on the working
cylinder (1) with the aid of a fastening device (12, 13, 15). The working
cylinder (1) is provided in its interior with a heating device. The
fastening device (12, 13, 15) has at least one clamping ring (15) which
acts on the circumferential edge (16) of the printing or embossing
stencil (14) and clamps against the working cylinder (1).

Claims:

1-10. (canceled)

11. Printing or embossing unit, comprisinga working cylinder,a
back-pressure cylinder,at least one printing or embossing stencil,a
fastening device for the at least one printing or embossing stencil, anda
heating device provided in the interior of the working cylinder,wherein
the working cylinder carries each stencil on its circumference, in order
to emboss or to print, with the aid of said printing or embossing stencil
a web made from a flat material which is conveyed between the said
working cylinder and the back-pressure cylinder,wherein each embossing
stencil extends in each case only over part of the circumference of the
working cylinder and is held on the working cylinder with the aid of the
fastening device,wherein the fastening device comprises at least one
clamping ring which acts on the circumferential edge of the printing or
embossing stencil and clamps against the working cylinder.

12. Printing or embossing unit according to claim 11, wherein the
fastening device has two clamping rings which act on circumferential
edges of the printing or embossing stencil which lie opposite one
another.

13. Printing or embossing unit according to claim 11, wherein the
fastening device has fixing pins which penetrate fixing holes of the
respective printing or embossing stencil, wherein at least one of the
fixing holes being larger in the circumferential direction than the cross
section of the pin which penetrates the said hole.

14. Printing or embossing unit according to claim 13, wherein in each case
one fixing pin is offset in the circumferential direction with respect to
another.

15. Printing or embossing unit according to claim 11, wherein, in the
unheated state of the working cylinder, the clamping ring has a gap with
respect to the said working cylinder.

16. Printing or embossing unit according to claim 15, wherein. in the
unheated state of the working cylinder, the clamping ring has a gap with
respect to the stencil.

17. Printing or embossing unit according to claim 11, wherein at least one
of the parts which are clamped around by the clamping ring from the group
encompassing the working cylinder and the printing or embossing stencil,
is composed of a material with a greater coefficient of thermal expansion
than the material of the clamping ring.

18. Printing or embossing unit according to claim 17, wherein the
coefficient of thermal expansion of the material with said greater
coefficient of thermal expansion is greater by at least 25%.

19. Printing or embossing unit according to claim 17, wherein the clamping
ring is composed of a steel and in contrast the printing or embossing
stencil is composed of a non-ferrous metal.

20. Printing or embossing unit according to claim 19, wherein the clamping
ring is composed of a tool steel.

21. Printing or embossing unit according to claim 19, wherein the printing
or embossing stencil is composed of brass.

22. Printing or embossing unit according to claim 17, wherein the clamping
ring is composed of a tool steel and in contrast the working cylinder is
composed of chromium steel.

23. Printing or embossing unit according to claim 11, wherein at least two
printing or embossing stencils are fastened to the working cylinder
offset in the axial direction of the said working cylinder.

24. Working cylinder for a printing or embossing unit, havingat least one
printing or embossing stencil,a fastening device for the at least one
printing or embossing stencil, anda heating device provided in the
interior of the working cylinder,wherein each printing or embossing
stencil extends only over part of the circumference of the working
cylinder and is held on the working cylinder with the aid of the
fastening device,wherein the fastening device has at least one clamping
ring which acts on the circumferential edge of the printing or embossing
stencil and clamps against the working cylinder.

25. Working cylinder according to claim 24, wherein the fastening device
comprises two clamping rings which act on circumferential edges of the
printing or embossing stencil which lie opposite one another.

26. Working cylinder according to claim 24, wherein, in the unheated state
of the working cylinder (1), the clamping ring has a gap with respect to
the said working cylinder.

27. Working cylinder according to claim 24, wherein at least one of the
parts which are clamped around by the clamping ring, that is to say the
working cylinder and the printing or embossing stencil, is composed of a
material with a greater coefficient of thermal expansion than the
material of the clamping ring, the clamping ring being composed of a
steel and in contrast the printing or embossing stencil being composed of
a non-ferrous metal and in contrast the working cylinder being composed
of chromium steel.

Description:

TECHNICAL FIELD OF THE INVENTION

[0001]The invention relates to a printing or embossing unit having the
features of the precharacterizing clause of Claim 1, and to a working
cylinder having the features of the precharacterizing clause of Claim 9.

PRIOR ART

[0002]A printing or embossing unit of this type according to the
precharacterizing clause of Claim 1 is known from DE 196 12 314. The
printing or embossing unit described there has two cylinders, of which
one working cylinder carries at least one printing or embossing stencil
on its circumference, in order to emboss or to print, with the aid of the
said at least one printing or embossing stencil, a web made from a flat
material which is conveyed between the said working cylinder and a
back-pressure cylinder. The embossing stencil of DE 196 12 314 extends
both in the axial direction of the working cylinder and in the
circumferential direction of the working cylinder, in each case only over
part of the working cylinder. It is held on the working cylinder with the
aid of a fastening device which comprises two holding rings which are
arranged to the left and the right of the embossing stencil and in which
holes are provided in their longitudinal direction and threaded holes are
provided which are aligned with the former, cylinder pins which are
guided in the holes engaging into clamping faces of the embossing stencil
which are cams which are arranged transversely with respect to the
circumferential direction. On its circumference, the working cylinder has
a heating device which is arranged between the said holding rings. The
cylinder pins are held by threaded screws which are arranged in the
threaded holes. The fastening device therefore has two clamping rings
which act on the circumferential edge of the printing or embossing
stencil and clamp against the working cylinder. The description of the
adjustment by means of loosening and tightening of the threaded screws
counter to springs provided between them and the cylinder pins shows the
complexity of the adjustment. It also requires a pin/hole combination, in
order to adjust the inserted embossing stencil at the correct provided
position in the circumferential direction.

[0003]EP-A-1 393 904, for example, has disclosed another embossing device.
Here, a plurality of stencils are fastened to a working cylinder offset
in the axial direction and in the circumferential direction, by means of
pins or screws and by means of wedges which act on oblique
circumferential edges of the stencil. This type of fastening is not
always reliable and, moreover, is relatively difficult to produce.

[0004]A simple fixing device of embossing stencils on a working cylinder
is shown in U.S. 2005/081730, in which a heatable steel cylinder is
surrounded by a slotted aluminium hollow cylinder which substantially
encloses the said steel cylinder. Different embossing cylinders made from
brass are pushed onto the said slotted aluminium hollow cylinder. As a
result of the greater expansion of aluminium, the brass embossing
cylinder is clamped on the steel working cylinder. An adjustment of the
position of the embossing cylinder in the axial direction or in the
circumferential direction is not provided.

SUMMARY OF THE INVENTION

[0005]Proceeding from this prior art, the invention is therefore based on
the object of finding a simpler fastening system for stencils which are
divided in the circumferential direction, and this is effected by the
characterizing features of Claim 1. According to the invention, only the
clamping ring therefore need be pulled over the circumferential edge, two
clamping rings which act on circumferential edges of the printing or
embossing stencil which lie opposite one another expediently being
provided.

[0006]It was necessary in the prior art to connect the respective stencil
relatively rigidly to the working cylinder. In view of the fact that this
cylinder is heated, however, and thermal expansions therefore result, it
is more advantageous if, according to the invention, the fastening device
has pins which penetrate holes of the respective printing or embossing
stencil, preferably in each case one pin which is offset in the
circumferential direction with respect to the other, at least one of the
holes being larger in the circumferential direction than the cross
section of the pin which penetrates the said hole.

[0007]If a "clamping ring" is mentioned in the context of this invention,
it can be configured in a very wide variety of ways, for example also
with a slot which makes a compliance possible and extends approximately
parallel to the axis of the working cylinder or obliquely with respect
thereto. It is preferred, however, if the thermal expansion itself is
used for clamping, and it is advantageous for this purpose if at least
one of the parts which are clamped around by the clamping ring, that is
the working cylinder and/or the printing or embossing stencil, is
composed of a material with a greater coefficient of thermal expansion,
for example greater by at least 25%, than the material of the clamping
ring.

[0008]This results in an automatic mechanism which applies stress to the
parts only when the working cylinder or the printing or embossing unit is
in operation and heated, whereas the stressing is triggered automatically
in the other case.

[0009]This can be realized in such a way that the clamping ring is
composed of a steel, in particular a tool steel, and in contrast the
printing or embossing stencil is composed of a non-ferrous metal, in
particular of brass, and/or in such a way that the clamping ring is
composed of a tool steel, and in contrast the working cylinder is
composed of chromium steel. It is to be mentioned here that the stated
pairing of materials having different coefficients of thermal expansion
can also be achieved with other materials, for example by the use of
aluminium. However, the preferred chromium steel for the working cylinder
is of greater strength and is therefore more suitable for the present
purposes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]Further details of the invention result using the following
description of one preferred exemplary embodiment which is shown
diagrammatically in the drawing, in which:

[0011]FIG. 1 shows a diagrammatic view of a printing or embossing unit,

[0012]FIG. 2 shows an enlarged perspective view of the working cylinder
and the back-pressure cylinder,

[0013]FIG. 3 shows a section through a printing or embossing stencil in
contact with the surface of the working cylinder and fixed by two
clamping rings,

[0014]FIG. 4 shows a perspective view of a printing or embossing stencil
with fastening holes and pins, and

[0015]FIG. 5 shows an enlarged perspective view of the working cylinder
and the back-pressure cylinder according to a further exemplary
embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EXEMPLARY EMBODIMENTS OF THE INVENTION

[0016]FIG. 1 diagrammatically shows a single printing or embossing unit
having a working cylinder 1 and a back-pressure cylinder 2 behind a
bearing plate 3 with a bearing block (indicated in FIG. 2) which is
carried by the bearing plate 3. The bearing plate 3 rests on an
approximately T-shaped bracket 4. In relation to FIG. 1, a web 5 to be
printed or to be embossed is pulled off from the left from a supply reel
(not shown), runs over a deflection roller 6 between the working cylinder
1 and the back-pressure cylinder 2, and is pulled off on the right-hand
side over a further deflection roller 7 to form a receiving reel (not
shown), as is known. It is clear that the web 5 is only one example and
that, if corresponding conveying devices are present, individual sheets
can optionally also be embossed or printed, the expression "web" of flat
material also including sheets of this type.

[0017]The printing or the embossing takes place in a known way by means of
a printing or embossing stencil (shown more clearly in FIG. 2) which is
fastened to the working cylinder, via a printing or embossing film 8
which runs from a supply reel 9 in the same direction and carries, for
example, a pattern to be printed on the web 5, a film to be transferred
or the like, which pattern or the like is transferred hot to the web 5
during passage between the cylinders 1 and 2, whereupon the empty
printing or embossing film 8 is pulled off upwards, sucked off, for
example, into a collecting container 10 and is optionally comminuted in
the process.

[0018]FIG. 2 shows the ratios of the working cylinder 1 and the
back-pressure cylinder 2 in a perspective view. Here, the working
cylinder is heated in a manner which is not shown here but is known per
se, which preferably takes place in such a way as is described in claim
22 of German Laid-Open Specification No. 10 2005 054766, namely by a
stationary heating cartridge which serves substantially as an axle and
penetrates an opening 11 of the working cylinder 1.

[0019]The working cylinder 1 has a row of elevated printing or embossing
stencils 14 on its circumference, for example for printing labels, which
printing or embossing stencils 14 are shown partially in FIG. 2 as
separate parts. Each of these printing or embossing stencils 14 has the
printing pattern (the letters PGS here) in an elevated manner, that is to
say protruding from the stencil material. Since each of these stencils 14
extends only over part of the circumference of the working cylinder 1,
for example with approximately 120 degrees over three or with
approximately 180 degrees over two, it is necessary to fix them in their
position relative to the working cylinder 1. For this purpose, two
measures are preferably provided. Firstly, each of these printing or
embossing stencils 14 which reach only over a part region of the
circumference of the working cylinder 1 has fixing holes or positioning
holes 12, into which fixing pins or, more precisely, positioning pins 13
engage. FIG. 4 shows this configuration on a larger scale. According to
the latter, it can be seen that the positioning holes 12 are somewhat
larger than the diameter of the pins 13. Only one of the positioning
holes 12a is expediently of larger configuration, namely as a slot, in
order for it to be possible for thermal expansions to be compensated for.
This positioning-hole/positioning-pin arrangement serves only to fasten
the stencil 14 in its circumferential direction in an axial groove 22. In
contrast, it is fixed in its axial direction in each case by at least one
clamping ring 15, advantageously by two clamping rings 15 which lie
axially opposite one another as shown in FIG. 2, which expediently
acts/act on a thinned edge piece 16 of the stencil. Secondly, it is clear
that only a hook can also be provided instead of the fastening device 12,
13 or instead of the pin 13, whereas the pairing 12a, 13 ensures the
movability as a consequence of thermal expansion along the circumference
of the working cylinder 1.

[0020]FIG. 3 shows the ratios on an enlarged scale. Whereas the stencil 14
bears against the surface of the working cylinder 1 and is positioned and
fixed in the circumferential direction by means of the fastening
arrangement 12, 13 which can be seen from FIG. 4, in each case one
clamping ring 15 is pushed over its edges 16 on at least one side,
preferably on both sides. This is facilitated particularly by the fact
that, in the unheated state of the working cylinder 1, there is
preferably a gap s between the internal diameter of the clamping ring and
the external diameter of the working cylinder 1. There can also be a
small gap (not shown here) between the external diameter of the
respective edge 16 and the internal diameter of that section of the
clamping ring 15 which acts on this edge 16.

[0021]On its side which faces the embossing stencil 14 during use on the
working cylinder, each clamping ring 15 has a radially inwardly oriented
recess 25. Where, on the side which faces away from the embossing stencil
14, the side wall 35 comes up to the external diameter of the working
cylinder 1 apart from the gap s, there is a negative step with respect to
the embossing stencil 14, which negative step is substantially
complementary with respect to the lateral steps/thinner edges 16 of the
embossing-stencil elements 14. Here, the inner cylinder shell surface
which is directed opposite the working cylinder 1 is larger than the
outer cylinder shell surface of the embossing-stencil elements 14; in
other words, there is a step on one or both sides of the
embossing-stencil elements 14, which step can be pushed under the
holding-ring recesses 25.

[0022]The configuration of the L-shaped clamping rings 15 can also be
defined differently, so that each clamping ring has a profile which has
the entire height of the side wall 35, there being a protruding shoulder
55 at the greater diameter end. This shoulder 55 does not have to be of
continuous configuration, as is shown in the drawings; it can also
comprise tongues or angular sections of between, for example, 15 and 90
degrees with corresponding sections without a shoulder 55 of between, for
example, 15 and 90 degrees.

[0023]"Automatic" fastening of the clamping rings 15 to the working
cylinder 1 and/or to the stencil 14 can then be obtained by the
coefficient of thermal expansion of the clamping rings being selected to
be lower than that of the working cylinder 1 and/or of the stencil 14,
for example at least 25% lower. If, for instance, the clamping ring 15 is
composed of a steel, in particular a tool steel, and in contrast the
printing or embossing stencil 14 is composed of a non-ferrous metal, in
particular of brass, the latter will be expanded under the action of the
heating of the working cylinder 1 and the heat transfer to the stencil 14
to a greater extent than the clamping ring, with the result that the
latter clamps the edges 16 extremely firmly. Secondly, another result of
the material pairing of the clamping ring 15 made from tool steel and the
working cylinder 1 made from chromium steel is a more pronounced
expansion of the working cylinder in the radial direction, as a result of
which the gap s is reduced or, instead, the clamping ring 15 is seated
fixedly on the surface of the working cylinder 1. Both measures, namely
the utilization of the greater thermal expansion of the stencil 14 and
the working cylinder 1 compared with that of the clamping ring 15, are
expediently used together.

[0024]If the working cylinder 1 itself is heated, it expands to a greater
extent than the clamping rings 15 as a result of the described material
selection, with the result that the embossing-stencil elements 14 are
pushed radially to the outside and the lateral steps 16 of the
embossing-stencil elements 14 are clamped between the said outer shell
face of the working cylinder 1 and the inner circumferential faces 45 of
the clamping rings 15. As a result, the embossing-stencil elements 14 are
fixed radially in their position in the longitudinal direction of the
working cylinder 1. The axial positioning is fixed in advance with
respect to the longitudinal groove 22 by the positioning pins 13 in the
positioning holes 12, 12a.

[0025]Other materials with similar thermal expansion properties could also
be used per se, for example a working cylinder 1 made from aluminium;
however, it can be seen from FIG. 2 that a plurality of stencils 14 can
be provided in the axial direction of the working cylinder 1, in order
for it thus to be possible to obtain a plurality of labels next to one
another by transfer of a medium 17, for instance a gold foil, in the
region of the elevated letters ("PGS") to a flat substrate or a web 5.
Here, each circumferential row of stencils 14 is separated axially from
the adjacent stencil 14 by a spacer ring 19. It is clear that the
back-pressure cylinder 2 either has stencils 14a which are complementary
with respect to the stencils 14 and therefore have depressions where the
stencils 14 have elevations (for hot embossing), or the back-pressure
cylinder 2 has a compliant surface (for printing or gold embossing), into
which the elevations of the stencils 14 are pressed.

[0026]Essential aspects are the higher coefficient of thermal expansion of
the working cylinder 1 with respect to the clamping ring 15 and the
higher coefficient of thermal expansion of the embossing-stencil elements
14 with respect to the clamping ring 15, in order firstly to fix the
clamping ring itself on the working cylinder 1 and secondly to fix the
embossing-stencil elements 14 within the clamping ring. It is
advantageous here that no screws at all have to be used for adjustment,
but rather that the adjustment can happen automatically by, after a first
flange 21 which is fastened on the working cylinder--and optionally one
or more spacer rings 19, first of all a first clamping ring 15 being
pushed against the last spacer ring 19, and the individual
embossing-stencil elements or embossing-stencil sections 14 then being
pushed under its recess, which individual embossing-stencil elements or
embossing-stencil sections 14 are then covered on the other sides by a
second clamping ring 15. In a simple embodiment, only one of the clamping
rings 15 is configured with the projecting shoulder 55, whereas the other
clamping ring 15 is pushed flatly against the embossing-stencil sections
14. This is then possibly followed by a further spacer ring 19 and/or
further pairs of clamping ring 15/embossing-stencil sections 14/clamping
ring. Compression springs are then inserted in a known manner between the
last spacer ring 19 and the terminating flange 21, in particular guided
in corresponding openings of the latter, in order to hold the ring system
in a prestressed state before the heating of the working cylinder brings
about the described stressing as a result of different material
expansions.

[0027]It also becomes clear from the above text that, after the printing
or embossing unit is switched off and after the working cylinder 1 has
cooled down, the clamping rings 15 automatically release the edges of the
stencils 14 and/or the working cylinder 1 again and can therefore be
removed easily again.

[0028]FIG. 5 then shows an enlarged perspective view of the working
cylinder 1 and the back-pressure cylinder 2 according to a further
exemplary embodiment of the invention. Identical or similar features from
both exemplary embodiments are provided in each case with the same
reference numerals. A clamping ring 15/embossing-stencil elements
14/clamping ring 15 pair is shown here, a clamping ring 15 being pushed
with its edge 55 over the thinned edge section 16 of the
embossing-stencil elements 14, and the other clamping ring 15 being shown
at a spacing from it. No spacer rings 19 are shown. The positioning pins
13 cannot be inserted here into axial grooves 22, but rather in a
predefined pattern of setting positioning holes 23. Each
embossing-stencil element 14 is therefore positioned in a predefined
manner not only in the circumferential direction but also in an axial
orientation. The clamping rings 15 therefore carry out the function
directly and exclusively here of fixing the previously oriented
embossing-stencil elements 14, which once again improves the changeover
times for an apparatus of this type.